The present invention relates to a power window drive device for opening and closing a window of a motor vehicle with the use of a drive source such as a motor. More particularly, the invention relates to a power window drive device for driving a wire used for opening and closing the window.
FIG. 5 is a side view showing the overall construction of a power window drive device of a type with which the present invention can be used. A window opening/closing mechanism 1 is mounted inside the door of a vehicle in the area under a window. The window opening/closing mechanism 1 is provided with a rail 2 along which a slider 3 is slidable. A wire 4, coupled to the slider 3, is wound around pulleys 5 provided at the top and the bottom of the rail 2, as well as a drive drum 10 located at a mid portion of the rail. The window drive section 6 includes a motor 9 for driving the drive drum. When the motor 9 is driven, the wire 4 is moved by the drive pulley 10 so that the slider 3 vertically moves. A window glass 7 is attached to the slider 3. When the window glass 7 is vertically moved together with the slider 3, it opens and closes a window space defined by a sash. In FIG. 5, a position sensor 8 is driven by an arm 3a of the slider 3 to detect the position of a window glass 7.
In the window drive section 6, when the motor 9 is driven, a worm gear is turned to rotate a worm wheel. Accordingly, the drive drum 10, provided coaxially with the rotary shaft of the worm wheel, is turned through the rotary shaft thereof.
The coupling structure of the rotary shaft with the drive drum is illustrated in FIG. 6. In FIG. 6, the rotary shaft and drive drum are respectively designated by reference numerals 28A and 10A. As shown, an oblong part 42 of the rotary shaft 28A is inserted into a shaft hole 43 of the drive drum 10A that is also oblong in shape. A flange 44, extending outward from the outer surface of the rotary shaft 28A, abuts a part of the outer surface of the drive drum 10A. In this way, the shaft is positioned. The bottom end of the rotary shaft 28A passes through the drive drum 10A. A metal washer 45 is fitted on the tip of a part of the rotary shaft 28A that protrudes from the drive drum 10A. Further, a stopper member 46, such as a C ring, is fitted in a circumferential groove formed in the outer surface of the rotary shaft and located outside the stopper member 46 (when viewed in the axial direction of the rotary shaft). With this arrangement, the rotary shaft 28A is prevented from slipping out of the structure.
In the coupling structure thus constructed, the circumferential groove receiving the C ring 46 must be formed in the outer surface of the rotary shaft. As a result, the cost to work the rotary shaft for forming the groove is high.
In the coupling structure for coupling the rotary shaft 28A to the drive drum 10A, the drive drum 10A is made of synthetic resin. If the C ring 46 is brought into direct contact with the drive drum 10A, the drive drum 10A tends to be worn by the C ring 46. To avoid wear of the drive drum 10A, the metal washer 45 is inserted between the drive drum 10A and the C ring 46. In this respect, the number of required parts is increased and the cost of manufacture is also increased. For the same purpose, in the rotary shaft of the power window drive device, an additional C ring (not shown) is provided in the portion of the rotary shaft where it is coupled to the worm wheel. Thus, two C rings must be mounted in assembling the power window drive device, making the assembly work inefficient.
To couple the drive drum 10A to the rotary shaft 28A, the oblong part 42 of the rotary shaft 28A (of the worm wheel) is inserted into the shaft hole 43, also oblong in shape, of the drive drum 10A. With this coupling structure, the rotational force generated therebetween is concentrated on the planar portions of the oblong shaft hole. In an extreme case, the shaft hole 43 of the drive drum 10A made of synthetic resin can be damaged, making the rotational coupling of these members poor.
Since the bottom end of the rotary shaft protrudes from the drive drum, the size of the structure as viewed in the axial direction is increased. This results in increase of the thickness of the body case 11A forming the window drive section 6.